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28 Cards in this Set
- Front
- Back
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GI:
Pelvic Nerve Innervation |
lower large intestine
rectum anus |
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GI:
Vagus Nerve Innervation |
Espophagus
Stomach Pancreas Upper Large Intestine |
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GI Plexus
1. Submucosal (Meissner's) 2. Myenteric (Auerbach's) |
receive input from both Symp and Para
1. Submucosal: secretion and blood flow; receives sensory input from chemoR and mechanoR in GI tract 2. Myenteric: motility of GI smooth muscle |
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Gastrin:
Action |
secreted by G cells of stomach antrum
1. inc. H+ secretion by parietal cells 2. trophic effect on gastric mucosa |
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Gastrin:
Secretion Stimuli |
Secreted by G cells in response to meal:
1. small peptides and aa in stomach 2. distension of stomach 3. vagal stimulation via GRP |
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Gastrin:
Inhibition |
1. H+ in lumen (negative feedback)
2. Somatostatin |
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CCK:
Action |
secreted by I cells of duod/jejunum
1. gallbladder contraction, relaxation of spincter of Oddi→bile secretion 2. pancreatic EZ secretion 3. potentiate secretin-induced stimulation of pancreatic HCO3- secretion 4. trophic effect on exocrine pancreas 5. inhibit gastric emptying 6. receptive relaxation: inc. distensibility of stomach for food |
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CCK:
Secretion Stimuli |
1. small peptides, aa
2. fatty acids and monoglycerides *BUT NOT triglycerides b/c cannot cross intestinal cell membrane →fatty meals slow gastric emptying to allow for more time intestinal digestion/absorption |
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Secretin:
Action |
released by S cells of duodenum; homologous to glucagon
1. pacreatic HCO3- secretion; trophic effect on exocrine pancreas 2. inc. bile production and liver HCO3- and H20 secretion 3. inhibit parietal cells |
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Secretin:
Secretion Stimuli |
1. H+ in duodenum
2. Fatty acids in duodenum |
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GIP:
Action |
secreted by duodenum/jejunum; homologous to secretin, glucagon
1. stimulate insulin release (oral glucose more effective than IV glucose) 2. inhibit parietal cells |
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GIP:
Secretion Stimuli |
fatty acids
amino acids oral glucose (carbs) |
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GI Paracrines
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secreted by GI mucosal endocrine cells
1. Somatostatin 2. Histamine |
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Somatostatin
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-stim. by H+
-inhibited by vagal stimluation 1. Inhibits release of all GI hormones 2. Inhibits parietal cells |
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Histamine
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-secreted by mast cells
Increases gastric H+ secretion: 1. stimulates parietal cells (via H2 R-->inc. cAMP) 2. potentiates effect of gastrin and vagal stimulation |
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GI Neurocrines
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-released from GI tract neurons
1. VIP 2. GRP 3. Enkephalins |
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VIP: vasoactive intestinal peptide
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-released from mucosal and smooth mm neurons
1. relaxation, including LES 2. stimulates pancreatic HCO3- secretion, inhibits parietal cells *secreted by pancreatic islet cell tumors→pancreatic cholera (diarrhea) |
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GRP: gastrin releasing peptide
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-released from vagus nerves that innervate G cells
1. stimulates gastrin release from G cells |
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Enkephalins
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-secreted from nerves of mucosa, sm. mm
1. stimulate contraction of sm. mm 2. inhibit intestinal secretion of fluid and electrolytes *basis of opiates to treat diarrhea |
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Gastric Empyting:
INHIBITORS |
1. Fat: by stimulating CCK release
2. H+ in duodenum: via direct neural reflexes (H+ R in duodenum) |
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1. Gastroileal Reflex
2. Gastrocolic Reflex |
Presence of food in stomach:
1. triggers inc. peristalsis in ileum; relaxation of ileocecal sphincter (mediated by extrinsic ANS) 2. inc. motility of colon and inc. frequency of mass movements (mediated by paraS and CCK/gastrin) |
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Saliva:
Function |
Function:
1. Initial starch digestion (a-amylase) 2. initial TG digestion (lingual lipase) 3. lubrication 4. protection |
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Saliva:
Composition |
flow rate determines composition of saliva:
@ low flow rate: low osmolarity (low Na, Cl, HCO3; high K) @ hi flow rate: closest to plasma 1. high [K+, HCO3] 2. low [Na, Cl] 3. hypotonic 4. a-amylase, lingual lipase, kallikrein |
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Gastric H+ Secretion
Stimulation |
1. Vagal Stimulation:
a. directly (Ach stim. of parietal cell) b. indirectly (GRP stim. of G-cell) 2. Gastrin (via CCK-B R) 3. Histamine (released by ECL cells) |
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Aldosterone
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Stimulates:
1. ENac channels in the distal tubule 2. acinar ducts of the saliva 3. Na/K channels in the colon |
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Vibrio Cholera
Mechanism of Diarrhea |
Stimulates Cl- secretion
1. Cholera toxin turns on Gs 2. Inc. cAMP levels⟿Cl- channels open 3. Na, H20 follow Cl- into lumen⟿ Secretory diarrhea |
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Small Intestine
Absorbed substances |
1. Monosaccharides
2. Proteins (di/tripeptides faster than aa) 3. Lipids 4. Fat soluble vitamins 5. Ca 6. Iron Ileum: 1. Water soluble vitamins, B12 2. Bile Acids |
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GI:
Trophic Factors |
Gastrin: stimulate, pancreatic and GI growth (except esophagus and stomach antrum)
CCK, secretin: stimulate growth of exocrine pancreas |
